Load Testing Results

[mikereed100]

Have you done any testing on soft shackles using a double figure eight as the stopper?

[thinwater]

Originally Posted by mikereed100

Have you done any testing on soft shackles using a double figure eight as the stopper?

I've used both fisherman's and figure-8s for stropes. The reason I suggested the double or triple fisherman's is practical; it makes a nicer round knot that is easier to feed in and seems to retain in the loop better. I did strength test them in polyester, only to extend of proving that the knot will not slip through under load; as with soft shackles, the knot shears off. So long as the loop catches on the first cross strand of the knot, it will not slide off.

With a diamond knot, most folks draw them up very tight and then trim/melt the tails. With these other knots, it is handier, for me, to leave a longish tail which is used to pull the knot through. I use these as sail ties (fixed eye) and to secure covers, and the tail gives me something to pull on; a soft shackle without a tail is more difficult to work with in this sort of application (nothing to pull on, and the loop closes as you pull). Horses for courses.

While the tied loop looks loose, it is exactly the size of the knot and in practice the knot cannot get out. Sometimes it's handy and neat to make them from a single strand and replace the loop knot with a splice, particularly if working with single braid, though I'm not convinced this would work out with Amsteel.

[HappyMdRSailor]

Originally Posted by estarzinger

RE Palomar... You have a winner there. Thanks.

In endura12, breaking strength is 1510lbs (54% of rated strength) vs the figure 8 at 1144 (41%). That is a statistically significant gain.

That looks like a good 'replacement' for the buntline in tieing to shackles. It's only limitation is that you do need to be able to take the loop fully around the attachment - works for shackles but not for say installed padeyes.

Could you not bring the loop under the keel and over the stick????

[estarzinger]

I have tried to summarize what I have learned here :load tests I would be interested in any feedback, on what I wrote and on what you a have found interesting/new in the testing.

I did manage to do some nylon testing today, but there were no new 'surprises' - just like in dacron, the knots rated higher than I would have expected before this testing.

[estarzinger]

This is a bit harder to do accurately than I expected. But the bottom line is that Stayset is slightly lower stretch than the Samson double braids.

[B-Baysailer]

Hi evans I have been playing around with my fishing line tester that I made But I can only pull to about 500lb so i cant break hi loads . try doing a double palomar knot u should get a higher breaking load.Just wondering how do you hold the line when testing for strait line strength its hard to get it to brake in the middle of the line. Not to be picky but if the line strength it 2500 and the knot broke at 1510 isnt that a little over 60%.thanks ur doing good work

[estarzinger]

Originally Posted by B-Baysailer

Hi evans I have been playing around with my fishing line tester that I made But I can only pull to about 500lb so i cant break hi loads . try doing a double palomar knot u should get a higher breaking load.Just wondering how do you hold the line when testing for strait line strength its hard to get it to brake in the middle of the line. Not to be picky but if the line strength it 2500 and the knot broke at 1510 isnt that a little over 60%.thanks ur doing good work

I will test the double palomar . . .but it looks like it was designed to be more slip resistant rather than 'stronger'.

The 'official' way to hold the line to test straight line strength seems to be with a splice on each end. Or at least, that's how the rope companies seem to do it for their data sheets. Note: there does seem to be some ISO standard for line strength without splices. I don't know how that is done, but the 'spliced strength' is much more commonly used (at least in the US).

I tested the Palomar in endura braid which has a strength of 2800lbs. So, not to be picky , but 1510lbs in 2800lbs is in fact (as I wrote) 54%. But do please realize that there is about +-3-5% statistical variability (in each pull).

[B-Baysailer]

sorry my bad I thought it was 2500 .

[thinwater]

Originally Posted by estarzinger

... Note: there does seem to be some ISO standard for line strength without splices....

The line is wrapped around a large diameter drum and secured under a clamp, after several wraps. Sort of like using a winch. I've done this sort of testing with New England ropes. One down side is that samples need to be 6'.

When I test thread or small cord (to 170#) that is how I do it... sort of. Wrap the string around a pull-up bar at one end and a broom stick at the other, stand on an acurate annalog bathroom scale, and pull (subtract your own weight). For smaller stuff I use loops to get ~ 50-100 pounds. Repeat and you get a good number.

[estarzinger]

I was going to test some halyard shackle knots in dyneema double braid (dacron cover so we would get breaking strength and not just slipping). . . . however . . . . the cover is just tearing at the knot and then the dyneema slipping.

Bowline at 51% of rated strength
Buntline at 42%

Bowline:
Buntline:

This is with FSE Robline. I have some warp speed coming and will try it, But basically this seems to be about cover strength, which is an interesting aspect of high mod cored ropes that I have not seen examined closely.

But I am a bit puzzled by this - why is the cover breaking? It should not be taking any/much load. Is it being 'crushed' into failure?

------------------------
on another topic, with 5 pulls the palomar and double palomar both break at (statistically) the same load. The double is more secure in very slippery line.

[mikereed100]

Originally Posted by estarzinger

gripper hitches

1/2" dyneema single braid main line, with 3/16" dacron double braid gripper line (samson LS - rated at 1200lbs)

rolling hitch slipped at 200lbs
rolling hitch with 3 turns slipped at 370 lbs
prusik slipped at 860 lbs
Icicle hitch did not slip, broke at 900lbs

Interesting stuff. Like many, I use a rolling hitch to attach my bridle to my anchor chain. Formerly used a length of 10mm Spectra attached to the apex of the bridle with a Prussik. After sitting out a 50 knot blow I found that the rolling hitch, while not slipping on the chain, had almost pulled through. (I had a backup bridle attached to the chain as well). Since then I have used a loop of 10mm Spectra to tie the rolling hitch. My hope is that the increased internal friction of the doubled line will prevent the knot pulling through. I have a figure 8 on the bitter end now just in case.

[estarzinger]

The stretch characteristics of the two dyneema single braid lines (amsteel blue and endura12) are (statistically) identical (as closely as I could measure them).

[Paul Elliott]

Originally Posted by estarzinger

I was going to test some halyard shackle knots in dyneema double braid (dacron cover so we would get breaking strength and not just slipping). . . . however . . . . the cover is just tearing at the knot and then the dyneema slipping.

[...]

But I am a bit puzzled by this - why is the cover breaking? It should not be taking any/much load. Is it being 'crushed' into failure?

I'm just guessing here, but is the dyneema first slipping inside the cover? This would obviously load up the cover, and as the dyneema continues to slip the cover breaks.

[glenn.225]

Originally Posted by thinwater

I've used both fisherman's and figure-8s for stropes. The reason I suggested the double or triple fisherman's is practical; it makes a nicer round knot that is easier to feed in and seems to retain in the loop better. I did strength test them in polyester, only to extend of proving that the knot will not slip through under load; as with soft shackles, the knot shears off. So long as the loop catches on the first cross strand of the knot, it will not slide off.

With a diamond knot, most folks draw them up very tight and then trim/melt the tails. With these other knots, it is handier, for me, to leave a longish tail which is used to pull the knot through. I use these as sail ties (fixed eye) and to secure covers, and the tail gives me something to pull on; a soft shackle without a tail is more difficult to work with in this sort of application (nothing to pull on, and the loop closes as you pull). Horses for courses.

While the tied loop looks loose, it is exactly the size of the knot and in practice the knot cannot get out. Sometimes it's handy and neat to make them from a single strand and replace the loop knot with a splice, particularly if working with single braid, though I'm not convinced this would work out with Amsteel.

thinwater, thanks for the quick loops, I will be using them in future.


Evans, keep up the great work, the newer fibers are fantastic and your work is proof to the average guy.

[estarzinger]

Originally Posted by Paul Elliott

I'm just guessing here, but is the dyneema first slipping inside the cover? This would obviously load up the cover, and as the dyneema continues to slip the cover breaks.

Yes, that was my first thought and is logical . . . EXCEPT the piece I was testing was only 400mm between the two knots. So there was not a lot of room for relative slipping between the cover and core. Unless the core is slipping right thru both knots.

If internal slipping was a problem with 400mm, imagine what it would be on a 40m halyard!